The present invention relates to image intensifiers and, more particularly, to electron multipliers used therein.
Image intensifiers are used in night/low light vision applications to amplify ambient light into a useful image. FIG. 1 depicts a known image intensifier tube 100. In the illustrated image intensifier tube 100, photons impinge upon a photo-cathode 102, thereby generating electron/hole pairs. A microchannel plate (MCP) 104 is positioned to receive the electrons generated by the photo cathode 102. The MCP 104 generates an increased number of electrons for each electron received from the photo-cathode 102. A phosphor screen 106 is positioned to receive the increased number of electrons and produce an image for display by the image intensifier tube 100. The photo-cathode 102, MCP 104, and phosphor screen 106 are supported by a vacuum housing 108 that maintains gaps between these devices under vacuum to facilitate the flow of electrons therebetween.
Electron-bombarded devices (EBD) are capable of multiplying electrons. FIG. 2 depicts an EBD 200, which is based on a semiconductor structure having an input surface 202 and an emission surface 204 opposite the input surface 202. Accelerated electrons 206 impinge on the input surface 202 to produce an increased number of free electrons 208 within the semiconductor structure. The increased number of electrons 208 traverse the semiconductor structure between the input surface and the emission surface where they are emitted. Additional information regarding EBDs can be found in Reflection and Transmission Secondary Emission from Silicon by R. U. Martinelli (Appl. Phys. Lett., Vol. 17, Num. 6, pp. 313-314, 1970) and in Reflection and Transmission Secondary Emission from GaAs by R. U. Martinelli et al. (J. Appl. Phys., Vol. 43, Num. 11, pp. 4803-4804, 1972).
Because EBDs 200 are semiconductor structures, they can be inexpensively produced using mature, proven semiconductor fabrication technology and have low power requirements. However, EBDs typically have poor image transfer characteristics when used for electron multiplication.
Accordingly, an inexpensive, low power electron multiplier having improved image transfer capability is needed for use in devices such as image intensifiers. The present invention fulfills this need among others.
The present invention provides an image intensifier and an electron multiplication method and apparatus therefor. The method in accordance with the present invention includes creating an increased number of electrons within a semiconductor device having an input surface and an emission surface opposite the input surface and directing the increased number of electrons to an emission area for emission from the emission surface. The apparatus in accordance with the present invention includes a semiconductor structure having an input surface for receiving electrons and an emission surface opposite the input surface, the semiconductor structure generating an increased number of electrons responsive to the received electrons. The semiconductor structure is doped to direct the increased number of electrons to at least one emission area on the emission surface, each of the at least one emission areas associated with a corresponding region of the input surface.